Rotary tools, such as drills or routers, include a tool retainer or holder that non-rotatably secures a rotary bit (e.g., a cutting tool such as a drill bit or a router bit) to a driving device that rotates a drive shaft. The rotation of the drive shaft causes a corresponding rotation of the rotary bit; consequently, the clamping force of the retainer must provide sufficient gripping action of the bit. Otherwise, the bit will slip in its holder, resulting in poor tool performance, as well as creating a hazard to those working near the tool.
Bit retainer systems for woodworking, metalworking, and the like have been developed. Common types of bit holders include collet systems or chucks. Collets require a substantial amount of torque to be exerted on a threaded retainer or spindle in order to attain sufficient clamping force on the bit. This preloads the system such that the frictional engagement between the collet and the cutting tool limits movement therebetween.
FIG. 1 is a perspective view of a rotary tool 100 (e.g., a router) including a conventional bit retaining system. As shown, the rotary tool 100 includes a motor housing 105, a bit retaining assembly 110, and spindle lock assembly 115. The bit retaining assembly 110 includes a spindle 120 with a collet 125, and a collet nut 130 threadingly engaging the spindle 120. Rotating the collet nut 130 displaces the nut along the spindle axis, which, in turn, narrows and widens the opening of the collet 125.
The spindle lock assembly 115 selectively secures the spindle 120 to enable the rotation of the collet nut 130. Engaging an actuator 140 activates a lock that prevents the rotation of spindle 120, which in turn, permits the rotation of the collet nut 130 with respect to the spindle 120. In operation, a user first engages the lock assembly actuator 140 with one hand to secure spindle 120. Using a second hand, the user rotates the collet nut 120 with a wrench to widen (loosen) or narrow (tighten) the collet to remove or secure the bit as needed.
Thus, when changing the bit of a router, it is necessary to utilize two hands—one to engage the locking mechanism and one to tighten or loosen the bit within a router collet. It is often desirable to quickly attach the bit to the rotary tool or to quickly remove the bit from the tool. For example, several router bits may be needed throughout the course of shaping a single work piece with a router; consequently, it would be desirable to change the bits quickly and efficiently. This process of utilizing multiple hands for changing the bits is inefficient and thus undesirable because of the additional time and effort required for attaching the bits to and removing the bits from the collet. Furthermore, in order to attain the high torque necessary to achieve proper clamping force collet systems typically require the use of a nut wrench that rotates the collet nut to release or capture the bit. This use of conventional wrenches to displace the collet nut is not only cumbersome, but often proves ineffective since the effective clamping force is dependent on the torque applied by the individual operator, which varies from one person to another.
Therefore, there is a need for a bit retaining system for a rotary tool that is operated utilizing a single hand, and which provides adequate torque to non-rotatably retain a cutting tool (such as a router bit) with minimal force applied by an operator.